Sound-recording system



A 7, 1931. H. c. HUMPHREY SOUND RECORDING SYSTEM Filed Aug. 23, 1929 //v l/EN 70/? /7'. C. HUMPHRE) n ho /v57 Patented Apr. 7, 1931 q A UNITED STATES v HARTLEY o. UMPHREY, or NUTLEY, NEW. JERSEY, ASSIGNOB. TO ELECTRICAL 'nn- 7 SEARCH rnonno'rs mcg or NEW'YOBK, n. Y., A conrona'rron or DELAWARE cording devices.

PATENT o r cE SOUND-RECORDING SYSTEM Application filed. August 23, 1929. Seria1 No. 387,863.

g ,This invention relates to systems for producing photographic sound records and has for its object the provision of a monitoring system which may be switched to monitor on the output from the sound detector or to monitor on the modulated light. transmitted through the film during the recording,

To produce a satisfactory record of sound, it is necessary to have a complete absence of all undesired sounds at. the sound detector,

and to have the desired sounds reach the sound detector without distortion. The recording studio is commonly arranged with adjustable curtains so that the reflection from the surfaces of the studiomay be damped to give the correct time of reverberation for the sound detector used. The added damping tends to make the sound unnatural to an observer in the studio and renders it difficult to decide on the best arrangement to give a record that will produce a pleasing .efiect in a theatre. WThejpresent invention contemplates the provision of a monitoring room of such size and acoustical properties as to simulate the acoustic conditions of a sound picture theatre of average size, and equipped with a sound radiator of the type An observer in the so that the circuit to the sound radiator may be connected to the output of the sound detector or switched to monitor on the modulated light transmitted through the film during recording. visual indicator is provided in the momtorlng room to indicate when the output power from the sound detector approaches the value at which the record'- ing devices Will be overloaded and a control device is provided by which the observer can reduce the sound power supplied to the re- The monitoring circuit may be. connected tov the output of the sound detector while pre- H liminary tests are made of the performance to be recorded. During these tests, the best arrangement of the scoreand the performers may be determined, the damping of the studio adjusted to. produce a pleasing sound reproduction in the monitoring room and the sound power output of the sound detector adusted to a value that will not overload the recording devices. During the recording the monitoring circuit maybe switched to monitor on the -modulated light transmitted through the film during recording. .The

monitoringcircuit may be switched back at vided in the studio in which the sounds are produced. These sound detectors may be condenser type microphones or other suitable devices. If condenser type microphones are used small thermionic amplifiers 3, 4: may be provided to raise the output power of the microphone to a convenient value; The outputs from the microphones 1, 2 are fed .through a junction box 5 to the monitoring room. I e

The varying electrical "currents from the microphones 1,2 are combined in any desired ratio in connection circuits 6 and 7 which may be mixer circuits of the type described vin Broadcast Control Operation by Carl Dreher in the Proceedings of the Institute of ,which is preferablya gain control of the type described on page 216 offThe Thermionic Vacuum Tube by H. J. Van der .Bijl published 1920 by McGraw-Hill Book on, Inc.

239 West 39thStreet, New York city. By

means of this gain control. the monitoring observer can 7 control the energypassed to the amplifier. c j r The energy from the gain control 8 is amplifiedby the main amplifier 9 (which may b of any suitable type) and distributed by the conductors 10 and 11 to a plurality ofbranch circuits. A plurality of recording circuits Band 13 are provided. Each circuit comume indicating meter 21, to indicate when the output power from the sound detectors approaches the Value at which the recordingdevices 18 and 19 will be overloaded.

Also bridged across the conductors 10 and 11 is an artificial line 22, which may be a resistance network or a potentiometer similar to the gain control 8. The artificial line 22 terminates in the springs 23 and 24 of relay 25 and limits the power delivered to the monitoring circuit from conductors 10 and l l to the same value as the power delivered to the monitoring circuit from the other circuits which may be connected to the monitor'- ing circuit.

Incorporated in the recording machines 18 and 19 are photoelectric cells 26 and 27 which are excited by the modulated light passing through the film. The output currents from the photoelectric cells 26 and 27 are amplified in suitable amplifiers 28 and 291 The output circuit of amplifier 28 terminates'in springs 30 and 31 of relay 32. The output circuit of amplifier 29 similarly terminates in springs 33 and 34 of relay 32. Springs 33 and 34 of relay 32 normally make contact with springs 35 and 36 of the same relay which are connected to springs 37 and 38' of relay 25; Springs 37 and 38 of relay 25 normally make contact with springs 39 and 40 of relay 25. Connected to springs 39 and 40 of relay 25 is a suitable amplifier 41. The amplified currents from amplifier 41 are fed through a volume control 42, similar to gain control 8, to a sound radiator 43 in the monitoring room.

The output current from the'photoel'ectric cell 27, is amplified by amplifier 29 and conducted through springs 33 and 35 of relay 32, springs 37 and 39 of relay 25 through amplifier 41 and volume control 42 to the sound radiator 43 and back through volume control 42, amplifier 4'1, springs 40 and 33 of relay 25, springs 36 and 34 of relay 32, and

amplifier 29 to the photoelectric cell 27, causing the sound corresponding to the modulation of the light to be reproduced by the radiator 43. I

If the monitoring observer wishes to monitor on the sound being recorded in recorder 18, key 44 is depressed closing a circuit from battery 45 through key 44, winding of relay 32 to battery 45 operating relay 32. The operation of relay 32 breaks the connections between springs 33 and 35 and between springs 34 and 36, and connects spring 35 to spring 30 and spring 36 to spring 31 connecting the output of amplifier 28 to the monitoring circuit, and causing the sound corresponding to the modulationof the light to be reproduced by the radiator 43.

Operating key 46 closes a circuit from battery 45 through key 46, winding of relay 25 to battery 45 operating relay 25, breaking the connections at springs 39 and 37 and springs 40 and 38, and making connection between springs 39 and 23 and springs 40 and 24. This will connect the monitoring circuit to the output from the sound detectors and permit the monitoring observer to compare the output from the sound detector with the modulation of the light in the recording device.

The provision of a pluraliy of recording devices permits two identical records to be produced simultaneously. The one record may be taken, for example, on a regular film and the second on a film capable of rapid development. The second film may be developed during the recording, or immediately after, so that may be used to reproduce sound immediately, thus saving the time required to develop the regular negative and to print the regular positive. The director of the production can thus have the record reproduced immediately after the recording so that he may determine Whether the record is satisfactory before the performers have dispersed. Also, if desired, two records of the same sound may be made simultaneously, but having different power inputs to the recorders.

lVhat is claimed is:

1. In a sound recording system, in combination, a sound detector, means for amplifying the output of said sound detector, a plurality of unilaterally conductive recording circuits energized by said amplified output and each containing a sound recorder, monitoring means respectively responsive to said sound recorders, a monitoring circuit containing a sound reproducer, and relay means for connecting said monitoring circuit to one of said monitoring means and for disconnecting said monitoring circuit from said one of said monitoring means and connecting said monitoring circuit to another of said monitoring means.

2. In a sound recording system, in combination, a plurality of sound detecting devices respectively arranged to vary electrical currents in accordance with sound, means for combining said currents in a desired ratio, means for amplifying said combined currents, a plurality of devices for recording the effect of said combined currents, means including unilaterally conductive devices to prevent said recording devices from reacting on eachother, monitoring means respectively responsive to said recording devices, a monitoring circuit including a sound reproducer and relay means for connecting said monitoring circuit to one of said monitoring means and for disconnecting said monitoring circuit from said one of said monitoring means and connecting said mon itoring circuit to another of said monitoring means.

3. In a. sound recording system, in combination, a plurality of sound detecting devices respectively arranged to vary electrical currents in accordance with sound, means for combining said currents in a desired ratio, means for amplifying said combined currents, a plurality of devices for recording the effect of said combined currents, means including unilaterally conductive devices to prevent said recording devices from reacting on each other, monitoring means respectively responsive to said recording devices, a monitoring circuit including a sound reproducer, relay means for connecting said monitoring circuit to one of said monitoring means and for disconnecting said monitoring circuit from said one of said monitoring means and connecting said monitoring circuit to another of said monitoring means and other relay means for disconnecting said monitoring circuit from said monitoring means and connecting said monitoring circuit to the output of said amplifying means.

4. In a sound recording system, in combination, a plurality of sound detecting de vices respectively arranged to vary electrical currents in accordance with sound, means for combining said currents in a desired ratio, means for controlling said combined currents, means for amplifying said combined currents, meter means for indicating the power output ofsaid amplifying means, a plurality of devices for recording the effect of said combined currents, means including unilaterally conductive devices to prevent said recording devices from reacting on each other, means for individually controlling the energy supplied to each recording device, monitoring means respectively responsive tosaid recording devices, means for individually amplifying the output of said monitoring means, a monitoring circuit including an amplifier and a sound reproducer, relay means for connecting said monitoring circuit to the amplified output of one of said monitoring means and for disconnecting said monitoring circuit from said amplified output of one of said monitoring means and connecting said monitoring circuit to the amplified output of another of said monitoring means and other relay means for disconnecting said monitoring circuit from said monitoring means and con necting said monitoring circuit through an attenuating network to the output of said amplifying means.

5. The method of producing a photographic record of sound which comprises converting the sound energy into electrical energy varyingin accordance with sound, modulating light energy by means of said varying electrical energy, photographically recording said modulated light, reconverting a portion of said modulated light into electrical energy varying in accordance with said modulated light, actuating by said last mentioned electrical energy a sound radiator arranged to reproduce sound under acoustic conditions simulating the acoustic conditions of an average sound picture theatre, and comparing said sound with the sound produced by the said radiator when actuated bya portion of said first mentioned electrical energy.

In witness whereof, I hereunto subscribe my name.

HARTLEY C. I-IUMPHREY. 

